Offshore platform desulfurization: seawater compatibility treatment technology of magnesium hydroxide slurry
I. Unique challenges and breakthrough logic of offshore desulfurization
Offshore facilities such as offshore oil platforms and ocean-going ships face harsh desulfurization environments: high salt spray corrosion, scarce fresh water, and limited space. Traditional calcium desulfurization is difficult to adapt due to problems such as high reagent consumption and difficult sludge disposal. Taking a drilling platform in the South China Sea as an example, its diesel generator desulfurization system consumes more than 20,000 tons of fresh water annually, and the gypsum by-product cannot be reused due to the presence of chloride ions (Cl⁻＞0.5%), and the landfill cost is as high as 500 yuan/ton.
The innovative application of magnesium hydroxide slurry and seawater compatibility treatment technology is opening up a new path for offshore desulfurization. This technology achieves an ecological closed loop of "using the sea to treat sulfur" through three breakthroughs: seawater activation of magnesium hydroxide, dynamic stability of slurry, and resource utilization of by-products. Actual measurement data from a drilling platform in the Bohai Sea showed that after adopting this technology, the desulfurization efficiency reached 96%, the fresh water consumption was reduced by 85%, and the purity of the by-product magnesium sulfate was increased to 99.2%.
2. Core breakthroughs in seawater compatibility technology
1. Chemical wisdom of seawater activation of magnesium hydroxide
In-situ preparation: Directly use seawater to react with magnesium oxide powder to generate magnesium hydroxide slurry, eliminating the fresh water dissolution step. A platform in the South China Sea uses a dynamic vortex reactor, and the slurry maturation time is shortened to 20 minutes, and the concentration is stabilized at 12%-15%.
Synergistic effect enhancement: The natural alkalinity of seawater (pH 7.8-8.3) and the slightly alkaline nature of magnesium hydroxide (pH 10.3-11) form a buffer system to enhance the SO₂ absorption capacity. A case study of a cargo ship modification in the Yellow Sea showed that the desulfurization efficiency was 18% higher than that of a pure water system at the same dosage.
Salt crystallization resistance: Develop nano-scale dispersants to inhibit the agglomeration of magnesium hydroxide particles in a high-salt environment. Actual measurements on an ocean-going tanker showed that the slurry could operate stably for 2,000 hours without precipitation under a Cl⁻ concentration of 50,000 mg/L.
2. Engineering innovation of slurry circulation system
Multi-stage spray optimization: titanium alloy solid cone nozzle is used to achieve slurry atomization particle size <50μm at 3.5-4.0 standard atmospheric pressure, and the coverage rate is increased to 95%. After the transformation of a drilling platform in the East China Sea, the liquid-gas ratio was reduced from 8L/m³ to 3.5L/m³.
Dynamic anti-blocking design: ultrasonic anti-scaling module is implanted in the slurry pipeline to peel off crystals through high-frequency vibration. The operation data of a project in Bohai Sea shows that the system blockage frequency has dropped from 3 times a month to 1 time in half a year.
Intelligent switching mechanism: Based on the development of dual-mode control algorithm of DCS system, it can seamlessly switch to pure seawater desulfurization mode when magnesium oxide is exhausted, ensuring desulfurization efficiency >90%.
3. Marine ecological cycle of by-products
Marine-friendly conversion of magnesium sulfate: after the desulfurization product is separated by nanofiltration membrane, the concentration of direct discharge to the sea is controlled within 0.1‰, which meets the requirements of Class III sea areas in the "Seawater Quality Standard".
Ecological restoration application: High-purity magnesium sulfate is used to improve coastal saline-alkali land. Data from the Jiaozhou Bay test field show that the soil pH value has dropped from 9.2 to 7.5, and the yield of salt-tolerant crops has increased by 30%.
Hydrogen energy coupling potential: Exploring green electricity electrolysis of magnesium sulfate solution to produce hydrogen. Each ton of byproduct can produce 62m³ of hydrogen with a purity of 99.97%, providing a new path for offshore platform energy supply.
III. Engineering practice and benefit verification
Case 1: Desulfurization transformation of drilling platform in South China Sea
Process configuration: seawater activated pulping system + three-stage cyclone spray tower + DTRO membrane concentration unit
Operation data:
SO₂ emission concentration <35mg/m³, reaching IMO Tier III standard
Annual saving of 18,000 tons of fresh water, 40% reduction in operating costs
Annual income of magnesium sulfate byproduct exceeds 8 million yuan
Ecological gain: pH fluctuation in surrounding waters <±0.2, coral coverage rate increases by 1.5% annually
Case 2: Dual-mode transformation of Southeast Asian ocean-going cargo ships
Space optimization: vertical compact desulfurization tower is used, and the floor space is reduced by 60% compared with traditional systems
Intelligent control: implanting IoT sensors to monitor slurry stability and equipment corrosion rate in real time
Economic breakthrough: the comprehensive cost of voyage desulfurization is reduced from 12,000 to 5,200, and the investment recovery period is 2.8 years
IV. Future technology evolution direction
1. Breakthrough in materials science
Marine bio-based dispersant: Green dispersant prepared by extracting natural polysaccharides from seaweed, with a biodegradation rate of over 95%
Self-repairing anti-corrosion coating: Developing bionic mussel protein coating, with Cl⁻ corrosion resistance life extended to 15 years
2. Energy synergy network
Wave energy drive system: Integrate oscillating water column device to power pulping and spraying units, achieving zero external power consumption
Offshore carbon storage closed loop: Inject desulfurization byproducts into seabed strata, and each ton of magnesium sulfate can mineralize and store 0.3 tons of CO₂
3. Intelligent operation and maintenance upgrade
Digital twin warning: build a three-dimensional fluid model to predict abnormal slurry flow state, and the fault identification accuracy rate is >90%
Blockchain traceability: by-product ecological emission data is uploaded to the chain to meet the EU "Convention on Sustainable Development of the Ocean" certification
When the desulfurization tower of the drilling platform and the surging seawater achieve a delicate balance of chemical reactions, when the chimney emissions of ocean-going freighters and marine ecological restoration form a closed loop of value, the seawater compatibility technology of magnesium hydroxide slurry has gone beyond the scope of pollution control and become a new infrastructure for the blue economy. From the blue waves of the South China Sea to the Arctic route, from nano-scale dispersants to megawatt-level hydrogen energy devices, this technology is redefining the environmental protection logic of the marine industry-here, every drop of seawater is an ally of desulfurization, and every gram of magnesium sulfate is writing the symbiotic code between man and the ocean.